Method and system of subduct &amp; cable installation

ABSTRACT

A method and system of installing a cable into a duct, comprising increasing the cross-sectional areas of subducting provided in the duct, so as to allow the cable to be received into the subducting, and then decreasing the cross-sectional area of the subducting containing the cable so as to reduce the volume occupied by the subducting in the duct. Cables may be inserted into the subducting, for example, by forcing compressed gas through the subducting, which simultaneously inflates the subducting.

This invention relates to the installation of components and subductinginto main ducts. In particular, this invention relates to a method andsystem for installing a component into a duct, to a method and systemfor installing subducting in a main duct into which cables may beinserted, and to a subduct.

It is a common requirement, for example, for telecommunicationcompanies, to install cables into long ducts which may be part of anextensive installed duct network. Many such ducts have limited space forremaining cable installation due to existing installed cables, thereforerendering the installation process difficult. Installation costs areinherently high making duct space a potentially valuable asset. This istrue for both partially populated ducts and empty ducts.

A typical installation process can involve the use of compressed gas,which is forced into the duct to provide a viscous flow along the duct,which results in a distributed forward force on the cable beinginstalled. Often this is done in a subduct within the main duct tofacilitate the process. This type of process is generally used for theinstallation of optical fibre cables. A disadvantage of such a system isthat more duct space is used than if the cables were installed directly,without the subduct, as adequate space is required for airflow aroundthe cable to allow effective installation. This space is only requiredduring installation or removal of the cable.

The present invention is directed to overcoming or substantiallyameliorating the above problems.

According to a first aspect of the present invention, there is provideda method of installing a component into a duct, the method comprising:

-   -   increasing the cross-sectional area of subducting provided        within the duct, so as to allow the component to be received        into the subducting; and    -   decreasing the cross-sectional area of the subducting containing        the component, so as to reduce the volume occupied by the        subducting in the duct.

According to a second aspect of the present invention, there is provideda system for installing a component into a duct comprising:

-   -   subducting having a variable cross-sectional area;    -   means for increasing the cross-sectional area of the subducting        so as to allow the component to be received into the subducting;        and    -   means for decreasing the cross-sectional area of the subducting,        so as to reduce the volume occupied by the subducting in the        duct.

According to a third aspect of the present invention, there is provideda method of installing subducting into a duct, the subducting having avariable cross-sectional area, the method comprising:

-   -   inserting the subducting into the duct; and    -   decreasing the cross-sectional area of the subducting to reduce        the volume occupied by the subducting in the duct.

According to a fourth aspect of the present invention, there is provideda system for installing subducting into a duct comprising:

-   -   subducting having a variable cross-sectional area; and    -   means for decreasing the cross-sectional area of the subducting        to reduce the volume occupied by the subducting in the duct.

According to a fifth aspect of the present invention, there is provideda subduct, arranged such that:

-   -   the cross-sectional area of the subduct can be increased so as        to allow a component to be received into the subduct; and    -   the cross-sectional area of the subduct containing the component        can be decreased, so as to reduce the volume occupied by the        subducting.

The invention will now be described by way of example only withreference to the accompanying drawings, in which:

FIG. 1 is a cross-section of the subducting embodying the invention, asmanufactured in a pre-inverted state;

FIG. 2 is a cross-section of the subducting of FIG. 1 being inflatedwithin a main duct;

FIG. 3 is a cross-section of the subducting of FIGS. 1 and 2 in aninflated state within a main duct;

FIG. 4 is a cross-section of the subducting of FIGS. 2 and 3 installedin a main duct with one subduct in the inflated state;

FIGS. 5 a and 5 b are cross-sections of the subducting of FIGS. 2 to 4in which a multiple subduct is inflated and installed in the main duct,and a plurality of subducts are shown deflated after cables have beeninserted therein;

FIG. 6 a is a sectional view of installation equipment for installingthe subducting of FIGS. 1 to 5 in a main duct;

FIG. 6 b is a perspective view of the pressurised chamber forming partof the equipment of FIG. 6 a;

FIGS. 7 a and 7 b are cross-sectional views of the subducts shown inFIGS. 2 to 5 b in a high density cable installation with multiple andsingle cable capacity subducts inserted in the main duct;

FIG. 8 is a cross-section of a second subducting installed in a mainduct with a plurality of cables;

FIG. 9 is an enlarged, cross-sectional view of the second subducting ofFIG. 8; and

FIG. 10 is a cross-section of the second subducting in an inflated statein the main duct.

The subducting shown in FIG. 1 comprises a multi-subduct 1 embodying theinvention, comprising a number of subducts 2 connected together alongtheir length. The subducts 2 are shown in an inflated state in FIG. 1and are illustrated in an inverted (that is inside-out) state with thenormally inside surface forming the outer surface in this state. In thispreferred embodiment, the multi-subduct is manufactured in this inverted(inside-out) state.

The multi-subduct 1 is shown in FIG. 2 in an uninflated state and in theprocess of installation into a main duct 4. The subduct 1 in theinverted state is partially inverted into the main duct 4. As thesubduct 1 is installed, it is turned inside out thereby forcing theoutside surface in this state (which is the normally inside surface 5)to become the inside surface, and the normally outside surface 6 tobecome the outer surface. This process is described in detail below.

FIG. 3 shows a multi-subduct 1 installed within a main duct 4 with theindividual subducts 2 of the multi-subduct 1 inflated.

FIG. 4 shows the multi-subduct 1 installed in the main duct 4 in itsgenerally uninflated state, but with one subduct 7 inflated as the cable8 is being installed through the centre thereof. Other cables 10 areshown installed in other sub-ducts 2 located within the main duct 4.

A plurality of fully populated multi-subducts 1 may be inserted into themain duct 4, as shown in FIGS. 5 a and 5 b.

The installation equipment 20 for use in the installation of the ductingembodying the invention is shown in FIGS. 6 a and 6 b. The equipmentcomprises a pressurised chamber 22 containing a multi-subduct 1 to beinstalled. The multi-subduct 1 is coiled in its inverted (inside-out)state within the pressurised chamber 22, and a gas supply 24 isconnected to an inlet of the pressurised chamber 22. A safety valve 26is also connected to the pressurised chamber 22. A delivery tube 28 isconnected to an outlet of the pressurised chamber 22. A free end of themulti-subduct 1 is clamped using a clamp 30 to the free end of thedelivery tube 28.

The pressure of the gas in the pressurised chamber 22 forces themulti-subduct 1 in the pressurised chamber out through the delivery tube28 and into the main duct 4, turning it inside out in the process suchthat the normally inside surface 5 is the inside surface and thenormally outside surface 6 forms the outer surface.

FIG. 7 a shows a multi-subduct 40 being inserted into a main duct 4 inwhich there are already installed a number of cables 10 located withininstalled subducts 1 which are in the uninflated state.

FIG. 7 b shows single subducts 42 being inserted into a main duct 4 inaddition to existing multi-subducts 1 which have already been installedin the main duct 4 and are now in the uninflated state. Such aconfiguration is particularly advantageous in situations where there isinsufficient room in the main duct 4 to accommodate multi-subducts.

The method of installing ducting will now be described by way ofexample.

When manufactured, the single subduct 42 or multi-subduct 1 is producedinside out with its normally inside surface forming the outer surface.This enables the subducting to be installed by inverse inflation, whichinvolves blowing the subduct or multi-subduct into a main duct 4 andturning it inside out in the process.

The single subduct 42 or multi-subduct 1, as manufactured, is coiled andis placed in the pressurised chamber 22, as shown in FIGS. 6 a and 6 b.One end of the subduct 42 or 1 is fed through the delivery tube 28 andis then folded back over the free end of the delivery tube and clampedthereto, using a clamp 30. Compressed gas is blown into the pressurisedchamber 22 from a compressed gas supply 24 and this raises the pressurein the delivery tube 28 connected thereto, forcing the subduct ormulti-subduct 1 out of the pressurised chamber 22 and down the deliverytube 28, turning it inside out in the process as it passes outside thedelivery tube, as shown in FIGS. 2 and 7 a. The subduct 42 or 1 is thenfed into the main duct 4 and is forced therealong to the desired lengthor position, whilst continuing to be turned inside out as it moves alongthe main duct 4.

Removing the pressure and disconnecting the subduct 42 or 1 from thepressurised chamber 22 causes the ducting to collapse, for example, dueto gravity, as shown in FIGS. 4, 5 a, 5 b, 7 a and 7 b. Cables 8 maythen be inserted in each subduct 1 or 42 and fed along the subduct byblowing compressed gas through this subduct to inflate it and provide aviscous flow through which the cables 8 can propagate. Once the cables 8are inserted into the subduct 1 or 42, the gas pressure is removed andthe subduct 1 or 42 collapses around the cable 8 as it deflates, asshown in FIGS. 4, 5 a, 5 b, 7 a and 7 b.

Multi-subducts of the type illustrated, for example, in FIGS. 1, 3, 5 a,5 b, 7 a and 7 b can be inserted, but if there is insufficient room inthe main duct 4 to accommodate such multi-subducts, single sub-ducts 42may be used to fill the remaining spaces, as shown in FIG. 7 b.

Various modifications may be made to the present invention, for example,whilst the embodiments described above refer to increasing thecross-sectional area of the subduct by application of an additional flowof compressed gas, the area could be increased by the gas flow which isused for the insertion of the cable into the subduct.

FIG. 8 shows a second type of subducting, comprising a single subduct50, installed in a main duct 4 containing a plurality of cables 10.Subduct 50, is illustrated in cross-section in a state immediatelyfollowing the process of installation of the subduct. It will beunderstood that the longitudinal axis of the subduct extendsperpendicularly into and out from the paper, i.e. substantially parallelto the longitudinal axes of the main duct 4 and cables 10. An enlargedview of the cross-section of subduct 50 is shown in FIG. 9.

Subduct 50 has been formed during manufacture into the tightly rolledconfiguration shown in FIG. 9. As such, the subduct takes up only theminimum volume possible within the duct 4. Subduct 50 is held in thisrolled configuration by means of a retention seal 51 runningsubstantially along the whole length of the subduct, and therebypreventing the subduct from unravelling (i.e. unrolling).

Installation of the subduct 50 into the duct 4 is by means of anystandard known method in the field, namely by pulling in using a rope orby attaching to a pneumatic duct motor. Once installed, the subduct 50can remain in the rolled configuration for as long as necessary untilrequired.

When it is desired to install a component, such as a cable, into theduct 4, a supply of pressurised gas is connected so as to inflate thesubduct 50 into the inflated state illustrated in FIG. 10, into whichthe cable can be received. Initially, sufficient pressurisation of thesubduct 50 must occur so as to break the retention seal 51, therebyallowing the subduct 50 to unravel from the spiral configuration andfully inflate, thereby substantially increasing in cross-sectional area.A cable is inserted into the subduct under the action of blowingcompressed gas through the subduct, simultaneously causing the subductto inflate and providing a viscous flow through which the cablepropagates. After installation of the cable, the pressurised gas supplyis removed, and the subduct 50 allowed to deflate and collapse under theinfluence of gravity.

The action of the subduct 50 collapsing when the pressurised gas supplyis removed causes a significant reduction in the volume taken up by thesubduct 50 compared with its previous inflated state. Advantageouslythis means that significantly more cables can be installed into a ductthan would otherwise be the case with solid subducting. Additionally,the tightly wound configuration of the manufactured subduct 50 meansthat a plurality of subducts can be inserted into the duct 4, all intheir rolled configuration, in advance of the cables, and then onlyinflated individually as needed.

Although the embodiment of FIG. 9 is shown in a generally spiral-shapedconfiguration, further variations are envisaged. The subduct may insteadbe concertinaed, or otherwise folded, or in part folded and partiallyrolled in any suitable configuration which allows ease of unravelling(i.e. unrolling or unfolding as necessary) upon inflation using apressurised gas supply. In addition, the retention seal 51 may byreplaced by a plurality of tags spaced at intervals along the length ofthe subduct, or retention means which encircles the circumference of therolled subduct, so long as such retention means are arranged to breakunder sufficient pressurisation of the subduct.

Although the duct shown in FIG. 8-10 comprises a single bore subduct,this could alternatively be provided as a multiple-bore subduct, therebyreducing the number of subduct installations required.

Still further modifications may be made to the embodiments describedherein. Whilst the variation of cross-sectional area of subducting hasbeen described as being a result of using a highly flexible materialwhich can be inflated using compressed gas and which naturally deflatesdue to gravity, the increase in cross-sectional area may also beachieved by using mechanical expansion or material expansion of thesubduct.

The system and method embodying the invention is particularlyadvantageous as it can replace traditional solid subducts used, forexample, in the installation of fibre cables in cabling networks. It isalso advantageous in situations where existing ducts are alreadyinstalled and new subducting is required to be inserted. The fibre countwithin existing ducts may be increased either by replacement of theinstalled cable with a multi-subduct embodying the invention, oraddition of subducts embodying the invention to the existing installedcable network. The bore diameter of the subduct embodying the inventionmay be chosen to best fit the cables to be installed. Such cables maybe, for example, traditional blown cables or micro cables. A particularadvantage of the subducting embodying the invention over traditionalsubducting is the reduction in duct space used by each installed cable.Furthermore, the invention enables cable installation into heavilycongested ducts resulting in a reduction in the required duct buildalong existing duct routes.

Thus the embodiments of the invention have considerable economicaladvantages and the advantage of ease of insertion.

The subducting embodying the invention may be formed of highly flexiblematerial, preferably of composite construction and which naturallydeflates due to gravity. Furthermore, the subducting embodying theinvention preferably has physical properties that enable a cable to beinstalled into it by the application of a flow of compressed air. Suchrequirements may include an ability to withstand pressurisation to atleast 10 bar, a natural tendency to deflate, a tendency to become rigidwhen pressurised, a low friction inner surface, and being resistant towear caused by contact with cables being installed. The sub-ducts ductsembodying the invention may be may be termed “Pneumatic SingleSub-ducts” (PSS) or “Pneumatic Multi-Subducts” (PMS).

In a further embodiment (not shown), subduct connectors may be used toassist in the construction of long lengths of subducting. Theseconnectors should be capable of withstanding the working pressure and bedesigned to cause minimal restriction to the subduct bore.

1. A method of installing a component into a duct, the methodcomprising: increasing the cross-sectional area of subducting providedwithin the duct, so as to allow the component to be received into thesubducting; and decreasing the cross-sectional area of the subductingcontaining the component, so as to reduce the volume occupied by thesubducting in the duct.
 2. A method of installing a component into aduct as claimed in claim 1, wherein the subducting is formed of aflexible material.
 3. A method of installing a component into a duct asclaimed in claim 1, wherein the step of increasing the cross-sectionalarea of the subducting comprises unravelling the material of thesubducting.
 4. A method of installing a component into a duct as claimedin claim 1, wherein the step of increasing the cross-sectional area ofthe subducting comprises mechanically expanding the subducting toincrease the area.
 5. A method of installing a component into a duct asclaimed in claim 1, wherein the step of increasing the cross-sectionalarea of the subducting comprises expanding the material forming thesubducting.
 6. A method of installing a component into a duct as claimedin claim 1, further comprising connecting the subducting to a supply ofcompressed gas, and activating the supply of compressed gas to force gasthrough the subducting to increase the cross-sectional area of thesubducting.
 7. A method of installing a component into a duct as claimedin claim 6, further comprising propagating a component through thesubducting via the action of the gas forced through the subducting.
 8. Amethod of installing a component into a duct as claimed in claim 1,wherein the step of decreasing the cross-sectional area comprisesallowing the subducting to collapse under gravity, or to deflate.
 9. Amethod of installing a component into a duct as claimed in claim 1,further comprising inserting the subducting into the duct via inversion.10. A system for installing a component into a duct comprising:subducting having a variable cross-sectional area; means for increasingthe cross-sectional area of the subducting so as to allow the componentto be received into the subducting; and means for decreasing thecross-sectional area of the subducting, so as to reduce the volumeoccupied by the subducting in the duct.
 11. A system for installing acomponent into a duct according to claim 10, wherein the subducting isformed of a flexible material.
 12. A system for installing a componentinto a duct according to claim 10, wherein the subducting comprises aplurality of subducts for receiving a plurality of components.
 13. Asystem for installing a component into a duct according to claim 10, thesystem further comprising a supply of compressed gas connectable to thesubducting for forcing gas through the subducting to increase thecross-sectional area of the subducting.
 14. A system for installing acomponent into a duct according to claim 10, further comprising a supplyof compressed gas connectable to the subducting for forcing gas throughthe subducting so as to propagate a component though the subducting. 15.A system for installing a component into a duct according to claim 10,wherein the material of the subducting is arranged in a configurationwhich unravels on the supply of pressurised gas into the subducting, soas to increase in cross-sectional area of the subducting.
 16. A systemfor installing a component into a duct according to claim 15, whereinthe subducting comprises retention means arranged so as to preventincrease of the cross-section area of the subducting by unravellinguntil a predetermined pressurisation of the subducting occurs.
 17. Asystem for installing a component into a duct according to claim 10,further comprising a supply of compressed gas connectable to thesubducting for forcing gas THROUGH! the subducting such that thesubducting may be inserted into a duct via inversion.
 18. A method ofinstalling subducting into a duct, the subducting having a variablecross-sectional area, the method comprising: inserting the subductinginto the duct; and decreasing the cross-sectional area of the subductingto reduce the volume occupied by the subducting in the duct.
 19. Amethod of installing subducting as claimed in claim 18, furthercomprising increasing the cross-sectional area of the subducting forreceiving components into the subducting before the step of decreasingthe cross-sectional area of the subducting to reduce the volume occupiedby the subducting in the duct.
 20. A method of installing subducting asclaimed in claim 18, wherein the subducting is formed of a flexiblematerial.
 21. A method of installing subducting as claimed in claim 18,wherein the step of increasing the cross-sectional area of thesubducting comprises mechanically expanding the subducting to increasethe area.
 22. A method of installing subducting as claimed in claim 18,wherein the step of increasing the cross-sectional area of thesubducting comprises expanding the material FORMING the subducting. 23.A method of installing subducting as claimed in claim 18, furthercomprising connecting the subducting to a supply of compressed gas, andactivating the supply of compressed gas to force gas through thesubducting to increase the cross-sectional area of the subducting.
 24. Amethod of installing subducting as claimed in claim 23, wherein the stepof activating the supply of compressed gas to force gas through thesubducting to increase the cross-sectional area of the subducting occurswhilst inserting the subducting into the duct.
 25. A method ofinstalling subducting as claimed in claim 18, wherein the step ofdecreasing the cross-sectional area comprises allowing the subducting tocollapse under gravity, or to deflate.
 26. A method of installingsubducting as claimed in claim 18, wherein the step of activating thesupply of compressed gas to force gas through the subducting includesturning the subducting inside out as gas is forced along the subducting.27. A method of installing subducting as claimed in claim 18, whereinthe step of turning the subducting inside out occurs as the subductingis being inserted into the duct.
 28. A system for installing subductinginto a duct comprising: subducting having a variable cross-sectionalarea; and means for decreasing the cross-sectional area of thesubducting to reduce the volume occupied by the subducting in the duct.29. A system for installing subducting into a duct as claimed in claim28, further comprising means for increasing the cross-sectional area ofthe subducting for receiving components into the subducting prior todecreasing the cross-sectional area of the subducting to reduce thevolume occupied by the subducting in the duct.
 30. A system forinstalling subducting according to claim 28, wherein the subducting isformed of a flexible material.
 31. A system for installing subductingaccording to claim 28, wherein the subducting comprises a plurality ofsubducts for receiving a plurality of components.
 32. A system forinstalling subducting according to claim 28, the system furthercomprising a supply of compressed gas connectable to the subducting forforcing gas through the subducting to increase the cross-sectional areaof the subducting.
 33. A system for installing subducting according toclaim 32, wherein the supply of compressed gas is operable to force gasthrough the subducting to increase the cross-sectional area of thesubducting whilst inserting the subducting into the duct.
 34. A systemfor installing subducting according to claim 32, wherein the supply ofcompressed gas is connectable to the subducting such that activation ofthe supply of compressed gas forces gas through the subducting causingthe subducting to turn inside out.
 35. A system for installingsubducting according to claim 34, wherein the subducting is arranged toturn inside out whilst the subducting is being inflated.
 36. A subduct,arranged such that: the cross-sectional area of the subduct can beincreased so as to allow a component to be received into the subduct;and the cross-sectional area of the subduct containing the component canbe decreased, so as to reduce the volume occupied by the subducting. 37.A subduct according to claim 36, in which the material thereof isarranged in a configuration capable of being unravelled so as toincrease the cross-sectional area of the subduct.
 38. A subductaccording to claim 37, in which the configuration of the material is agenerally spiral configuration.
 39. A subduct according to claim 36,further comprising: means for receiving a supply of pressurised gas intothe subduct, and arranged such that the cross-sectional area of thesubduct is increased by the supply of pressurised gas.
 40. A subductaccording to claim 36, for receiving in use a component introduced intothe subduct via the action of pressurised gas.
 41. A subduct accordingto claim 36, in which the material thereof is such that after thecross-sectional area of the subduct has been increased, the materialwill collapse under gravity so as to decrease the cross- sectional areaof the subduct.